Method of producing plaster materials



106. COMPOSITIONS,

COATING OR PLASTIC.

. Cros Reference D; DE F. CRANDELL METHOD OF @RODUCING PLASTER MATERIALS Filed Sept. 20, 1935 Jul '26, 1938. j

INVENTOR Dean D.Cmndafl.

Gil-w, @tvviMi RNEYS aminer Patented July 26, 1938 METHOD OF PRODUCING PLASTER MATERIALS Dean De Forest Crandell, Buffalo, N. Y., assignor to National Gypsum Company, Buifalo, N. Y.

Application September 20, 1935, Serial No. 41,497

1 Claim. (Cl. 83-73) This invention relates to an apparatus for and plaster building materials such as wall board, a method of preparing porous building materials, discharges into mixing chamber 6 preparatory more particularly vesicular plaster board where to being fed upon the forming belt or board belt The cementitious material from which the h r0 en eroxide is the material used to pro- I. 5 duce fie gas BuEBles inducing the porosim building product is to be made is discharged from of the individual pores.

ms container or reservoir 8 upon belt 5, the quantity In the preparation of porous cementitious prodbeing regulated by the speed of movement of ucts the strength of the product is very matebelt 5, and by regulating the size of discharge rially affected by the uniformity of distribution orifice 9 from reservoir 8, as by means of gate of the gas bubbles within the body of the porous valve I 0.

building structure and by the uniformity of size Where calcined gypsum stucco or laster is the cementitiofis material, it may be mixed with pre-.

The production of a porous product, therefore, depends upon the unidetermined quantities of water in reservoir 8 form distribution of the gas generating hydrogen before discharge upon belt 5, or, as the more genperoxide throughout the plastic mix prior to its set. dition where the same is to be mixed with fiber The atmosphere in gypsum plants and mills pulp for the production of wall board of the sois in general filled with fine flour or dust of called light weight type. In such a procedure ground gypsum so that fine orifices are prone the fibrous ul is prepared in a pulp heater and O to clog due to the accumulation of such dust in brmoper consistency and pulp content by addition of the amount of water required to be mixed with the calcined g fimd transferred to pulp storage or reservoir II and is fed from there upon the plaster l2 already discharged upon the endless belt. The rate of discharge of pulp I3 upon plaster I2 is suitably controlled as, for instance, by means of gate valve l4 controlling the size of orifice of chute IS.

The charge of plaster and wet pulp is carried along on endless belt 5 toward the point of hydrogen peroxide addition and the water from the pulp seeps through the plaster, hydrogen peroxide being then discharged upon this mixture from a discharge nozzle IS, the mixture thereafter being thoroughly agitated to distribute the pulp the fine openings or orifices. The hydrogen peroxide must therefore be added in a substantially large stream and yet in controlled and regulated amounts so as not to have an excess of this expensive chemical and such quantity that the individual pores are so large that the finished product possesses insufilcient strength for the desired use.

In accordance with the present invention hydrogen peroxide is added at a substantially constant rate to laster or stucco moved ata constant rate in constant amount upon an endless belt or other suitable contrivance.

An object of the present invention is, therefore, the provision of a method of adding hydrogen peroxide in controlled quantities to specified throughout the plaster by means of the rotating amounts of a plaster mix and in a manner promixing prongs ll. viding for uniform distribution of the hydrogen Hydrogen eroxide of any desirable or conperoxide throughout the mix. vement concenFration, such as 100 volume hy- Among other objects of the invention, is the drogen peroxide is contained in the storage tank provision of an apparatus with an orifice sufli- I8, and flows by means of gravity feed through ciently large as not to be clogged by mineral dust pipe I9 to filters 20, provided with a suitable or powder, and yet to provide for a constant rate filtering medium such as glass wool or the like, of discharge of hydrogen peroxide and a uniform to a reservoir 2| wherein a constant head of distribution of the peroxide with the plaster. hydrogen peroxide is maintained. The level of In the drawing Fig. l is a diagrammatic view of the peroxide in reservoir 2| is maintained at an apparatus suitable for use in the manufacture a constant head by means of float 23 attached of porous "gypsum products such as wall board, to valve 24 controlling the discharge of peroxide. while Fig. 2 is an enlarged view showing the Reservoir 2| is provided with a breather pipe means of discharging hydrogen peroxide to the 26 to compensate for the small rise and fall of mix. Fig. 3 is an enlarged view of the peroxide head of peroxide within the reservoir. Reserdistributing mechanism. voir 2| is also provided wiht a discharge exit Referring more particularly to the drawing, 21 adjacent its lower end to which is attached endless belt 5, adapted to carry ameasured charge a conduit 28 provided with needle valve 29 caof plaster mix suitable for the preparation of pable of being set to given a constant discharge eral practice, plaster is discharged in a dry coni orifice under influence of the constant head of peroxide contained in reservoir 2|. The orifice of valve 29 is sufficiently large to permit passage of whatever residual flour or dust may be picked up by the peroxide without danger of clogging at this point. After passing through the needle valve, the hydrogen peroxide is discharged from nozzle l6 provided with a discharge orifice 30 of relatively large diameter, which nozzle may be preferably made of glass.

Means are provided for oscillating discharge nozzle l6 laterally of endless belt -and the embodiment shown in the drawing comprises a pitman or rod 3| attached to discharge nozzle or tube l6 at a point below needle valve 29, pitman 3| being attached at 32 at its other end eccentrically of rotatable member 33 whereby upon rotation of member 33 the desired movement of nozzle l6 laterally of the belt is induced.

It will be seen that upon movement of the belt 5 at a constant rate and having a substantially constant load of material thereon, hydrogen peroxide is added or fed to the load upon the belt in such manner that a substantially uniform addition of peroxide is efiected per unit of time per unit of weight of charge. In order to render the distribution more uniform and to activate the liberation of oxygen from the peroxide, the mixture of plaster, water and peroxide is agitated by means of the prongs l1, discharged into mixing tank 6 and suflicient alkali added thereto to render the reaction of the mass alkaline. The whole mass is then agitated and mixed in mixing tank 6 prior to discharge thereof upon the board machine, where complete and uniform mixture of the peroxide and alkali throughout the mass is insured and evolution of oxygen occurs with the production of an aerated spongy plastic mass setting to a porous vesicular product having uniformly distributed pores of uniform size.

From the foregoing it will be seen that the present invention provides a method and apparatus by means of which a uniform distribution of hydrogen peroxide can be obtained throughout a plastic mix with the addition of peroxide in controlled amounts and under conditions where uniform distribution is a prerequisite to the production of an acceptable product.

What is claimed is:

The method of producing porous building materials from plaster, water and aqueous hydrogen peroxide which comprises moving a mix of plaster at a substantially constant rate, confining said plaster during its movement to a substantially constant width and depth, and adding to the upper surface of said plaster during its movement a substantially constant stream of water and hydrogen peroxide transversely of the direction of movement of said plaster, moving the stream at a substantially constant rate from one side to the other of said mix, and thereafter mixing said aqueous hydrogen peroxide with said plaster.

DEAN DE FOREST CRANDELL. 

